Thyroglobulin is of interest both as the predominant protein in the thyroid gland and as the site of thyroid hormone biosynthesis. Since hormone production in the thyroid must ultimately be controlled through changes in protein synthesis, it is of interest to study thyroglobulin synthesis. One approach to this problem is to isolate thyroglobulin mRNA and utilize this message for the translation of thyroglobulin in a heterologous cell-free system. This approach would lend itself to a systematic study of the control of thyroglobulin synthesis.